Self-energizing hydraulic leveling device for vehicle suspension



July 20, 1965 c. J. clsLo SELF-ENERGIZING HYDRAULIC LEVELING DEVI FOR VEHICLE SUSPENSION Filed Feb. ll, 1963 z w f W l Li..

ATIDRNEY United States Patent 3,195,877 SELF-ENERGIZING HYDRAULEC LEVELING DE- VICE @FR VEHCLE SUSPENSHON Casimer I. Cielo, Detroit, Mich., assigner to General Motors Corporation, Detroit, Mich., a corporation of Deiaware Filed Feb. Il, 1963, Ser. No. 257,629 6 Claims. (Cl. 267-60) This invention relates to vehicle suspension and more particularly to coil spring suspensi-on including associated apparatus for maintaining the vehicle sprung mass at a constant height irrespective of load imposed thereon.

An object of the invention is to provide an improved vehicle suspension.

Another object is to provide a coil spring suspension for vehicles incorporating hydraulically extensible spring seats which are automatically operable to vary the Vertical level of the upper end of the coil spring relative to the sprung mass of the vehicle so that compression of the coil spring resulting from increased load on the vehicle sprung mass is offset by increasing the vertical distance between the spring seat and sprung mass, thereby maintaining the sprung mass at a constant height irrespective of load.

7A further object is to provide an arrangement of the stated character wherein the displaceable spring seats incorporate height sensible automatic control means for f varying the displaced position of the extensible spring seats.

A still further object is to provide a device of the stated character in which the fluid pressure required to operate the displaceable spring seat is provided by pressure generating means contained entirely within the displaceable spring seat structure.

Yet a further object is to provide a structure of the stated character in which the pressure generating means is operated by random vertical deflection of the suspension structure,

Still a further object is to provide an in-line fluid flow control valve and iiuid pump having a common actuating element.

Still another object is to provide a self-energizing hydraulic leveling device in which both the energizing and leveling function are controlled by axial displacement of a common element.

A yet further object is to provide a hydraulically displaceable spring seat assembly having an internally disposed fluid liow control apparatus and iiuid pressure generating apparatus which are selectively operable as an automatic function of duration of displacement of the common element.

f In accordance with the general features ofthe invention, there is provided a hydraulically displaceable spring seat assembly wherein a piston rigidly secured to the vehicle sprung mass is surrounded by a generally cup-shaped cylinder adapted for telescoping movement relative thereto by introduction and evacuation of fluid between the piston and cylinder. The piston element carries an axially slidable spool valve and a fixed pump body disposed below and in axial alignment therewith. An externally actuated plunger element is reciprocably disposed concentrically within the spool valve and projects into the pump body. The piston element is cored to provide a fluid reservoir and formed with hydraulic fluid intake and exhaust passages arranged with reference to the spool valve so that flow of fluid into or out of the space between the piston and cylinder is controlled by the axial position of the spool valve relative to the piston. The pump body is arranged in series communication between the reservoir portion of the piston and an accumulator chamber,

ICC

also contained in the pist-on. Check Valve means associated with the pump body operate in concert with vertical displacement of the plunger tov provide more or less constant iiow of hydraulic fluid into an accumulator chamber contained within the piston. The accumulator chamber in turn is fitted with a flexible walled container filled with an inert gas under pressure which operates to exert a constant pressure on the fluid contained within the accumulator chamber to enable return thereof through the spool valve to dispiace the cylinder relative to the piston. To provi-de for discriminant operation of the spool valve, the latter is provided with a piston ange container within a dashpot cavity formed in the piston element which is ported in a manner requiring sustained displacement of the plunger to effect displacement of the spool by the resilient connection with the plunger. A resilient connection between the plunger and spool valve enables the latter to move in either direction from a neutral position without corresponding displacement of the spool as long as the duration of movement of the plunger is insufficient to override the retarding action of the dashpot. Accordingly, the spool valve is insensitive to short term displacement of the plunger which, therefore, functions under normal suspension only to operate the pump. However, upon sustained displacement of the plunger in either direction, the spool valve gradually moves from the neutral position to either an exhaust or intake position depending upon the direction of displacement, thereby causing the cylinder element to move either upwardly or downwardly as the case may be.

The foregoing and other objects, advantages and features of the invention will become more fully apparent as reference is had to the accompanying specification and drawing wherein:

FGURE l is a partially sectioned side elevational view of a portion of a vehicle suspension incorporating the invention;

FIGURE 2 is an enlarged sectional elevational View illustrating details of construction of the displaceable spring seat assembly shown in FIGURE l, the elements of the height control mechanism being shown in the neutral position obtaining under conditions of normal loading of the vehicle sprung mass;

FIGURE 3 is a fragmentary sectional view of a portion of FIGURE 2 illustrating the height control mechanism in the position occupied when the load on the sprung mass is greater than normal load; and

FIGURE 4 is a view similar to FIGURE 3 showing the relative position of the height control mechanism when the load on the sprung mass is less than normal load.

Referring now to the drawings and particularly FIG- URE l, the reference numeral 2 designates the longitudinally extending side rail of a vehicle frame which includes a trailing kick-up portion 4 overlying one end of a transversely disposed vehicle axle housing o. Rigidly connected to and depending from axle housing 6 is bracket 8, the lower end of which is pivotally connected at it) to the rear end of a longitudinally extending suspension control arm l2. The forward end of control arm 12 in turn is pivotally connected at le to an Outrigger bracket 16 mounted on the side wall of frame side rail 2. Rigidly mounted on the upper surface of control arm 12 longitudinally intermediate thereof is a fixed lower spring seat i8 Ion which is supported the Alower end of a coil spring 2i?. The upper end of spring 2t! in turn engages a flange 2?. formed on the upper end of cylinder portion Z4 of a vertically displaceable upper spring seat assembly 2d. Assembly Z6 includes `a piston element 28 disposed within cylinder portion 24, the upper end of which is rigidly secured in an opening 35) formed in an outrigger bracket 32 mounted on flange kick-up d in general vertical alignment with lower spring seat i8. The cylinder porc y v y tion 24 of assembly Zetelescopingly embraces piston 23 and is adapted to be displaeed'downwardly.relative to the piston fby introduction lof hydraulic uid in amanuer shortly to. be described,-so that as coil spring-2.9 is com-. pressed asa result. of. increased vloading .onrframe 2, the f flange Vportion 22. .ofV cylinderlldescends relativeto the frame an amount equal to theV compression deflection of ofthefcoil'springY and thereby restoresthe sprungr massY to the Vheight -Aobtaining under normal load conditions.` Exhausting of hydraulic fluid, in a manner also shortly.

tol be described, provides for .discharge of hydraulic V:lluid f upper and lower spaces 113 and 12u established at opposite sides of iiange piston 68.

c Yintroduced'in'to.thereservoir 36 and accumulator chamber 86, whichiluid thereafter. is` subjected to distribution and control in the following manner. 'With the vcylinder when the vehicle loading decreases, thereby allowingy y cylinder -24 to ascend as the 'coil yspring depression de- To automatically regulate the tlow'of hydraulic fluid and accomplish seli-energization of theiiluid system lin accordance with the invention, as :seen best in FEGURE 2, the piston element 28 is providedv with a coredup'pen portion [which includes 4an `annular reservoir :cavity 36 surrounding a -vertical passage comprising aligned bores 38, 40 and 4Z..of progressively.increasing diameter.l c ySlid-l ably. disposedwithin the bore Sis a plunger'element lid,V

the upper end of which is formed with a socket 45 pivotally engaged by the ball end 46 ofV anoperating leveri8v ulcrumed in an-eye S0 formedv on theitop walll 52 ofV piston element 2S. Plunger'element M 'extendsvdo'wn- 24 infully collapsed Vrelation to piston'ZS, assume that reservoiraifis substantially dlled .with hydraulic.iiuidV and that the. accumulator chamberV 86 'contains an additional quantityiof hydraulicfluid sutlicient to cause substantial further compression ofthe inert gas contained within Vchamber?V 1728. Underrthese circumstances, the pressure in chamber 128 exerts Ia corresponding pressure on-the fluid containedwithinchamber ycausing it to enter passagei/V Withf the Yspoolvalve .54v in the. neutral Vposition shownin"FGUlt'B'Z,Y -iiuid in passage v83 is permitted to emerge into groove 820i boreltl butremains .trapped therein.. (However, 'upon l. downward displacement lof jplungcr54, coilspring is'.momentarilycompressed further. as lthefwasher 58 movesdownwardlyf away from ilange 62 on spool valveil. The'additional compression wardly through bore 3i; into bore 4t), at which level itis 'Y surrounded .by an annular spool valve54 which slirdably interlits bore 4i). Impositive driving engagement between plunger 44 and` spoolvalve54 .iseiected by means of a coil spring Swhich surrounds plunger lll and isLdis-j4 thus `effected exerts diownwardlbiasing lfonce on the spool valvexthroughwasher 60 urging the spool valve towardlthe, position-.,shownin FIGUREJ.. 'The time posed in compression between an upper washenSS` and 'a lower washer 6d. Upper washer 53 abuts an inturned flange62 `formed on 4theupperend ofrspool 54, ywhile lower washervti abuts a snap ring 64 mounted'near the lower end 66 of spool 54.*. The lower extremity 66 of n spool 54 is formed with a radially outwardly extending flange piston' "slidably interiitting the -upper end of boref`42, .the purpose of which lwill appear shortly.V 'Ihe l Y lower end of plunger 44 carries a flexible piston ringv '76 -and extendsinto a' bore 72 formed in aV pump body rateres'ponsejof downward movement ofA spool Avalve 54 is fretar'ded Yby the dashpot ,action of iiange piston 68 niovingth-roughfthe ,hydraulicY fluid `medium' contained within theupper portion of b'or'e'42,'th' Vspeciiic Arate of responseheing determined. bythesize oflpassage' 116 f thr'oughfwhich transfer offfluid' ori-,the lowers-ide ofpisbon 6b towardthe upper'sidethereofY is infected. vAssoon as spool kvalve 54 reaches the. position` shownin FIGURE 3, rtheannula'r clearance '738 ,formedin vthe'spool valve .is throught' into partial registration with lower, groove -82 74 whichin .turn is .retained by snap ring -7i6'in the lower 'c portion-ofI bore 42 at a level permitting a predetermined range of y.vertical. travelof iiange` piston 68.-

. Intermediate'its endsrgspool valve VSLi-isy provided with an annular relief 7S which undernormal conditions occupi-esa vertical level intermediate a pair Yoi?V vertically spaced circumferential grooves 6) and SaZvformed in the and with passage "9,0, enabling lfluid pressurized inl passage 88 to move, therethrough vdownwardlythrough passage. 92 andf'e'me'rge in the space 94' between shoulder96 and 93./ As hydraulic.iluidentersthe; space,v cylinder 24 is yhydraulically,,displaced downwardly relative to piston 28 untilplunger 44'is returned Vto the vnormal position shown inf FLCYUWRIELLY at which time AspQOl valvel isfrestored to ytheneutral position bytheaction,oflcoil-spring 56.

wal-1 of bore 4th Groove 8@ establishes communication',

with :reservoir 36 by means of al port Sli, while groove S2 effects communication byjrneans of a passage' with an accumulator chamber 36 formed iny piston element 28.` belowrpump body 74. Apassage 90 establishes cdom-` munication with the interior of Vbore d@ intermediate ygrooves 8) and 82.' Passage 9@ in turn comrruinicates with a vertical passage Vgzrleading Vtofan annular space 94 located Vbetween the stepped bottom wall96 of 'cylin der 24and the shoulder 98 ofpiston 2S.

yFluid, communication between reservoir 36 and Vrac-ff cumulator 86 via pump body 74 is Veffected by apas'sage 1 190 formed in the wallportion surroundingbore 142V Upon upward-displacement ofrplunger-,54, coil spring 56 is momentarily cor/npressed 'further'asthe' washer 60 movesupwardlyaway .from snappring 64 on spool valve r54. v,The,-additional compression thuselfected exerts up. wardbiasing force 'onthespoolivalvejthroughwasher 5S andjlangeV ,zur'gingithe spool, valve toward Ythe position "shown in lIGURE 4.r Asrpreviously noted, the time rate response lof upwardv movement "of spoolvalve `54 is re-` tardedby. thedashpoll actionof flange piston68 moving 4through. tlieghydraulic liuidtmedium contained within the Y reachesthe positon shown in FIGUREA, thevclearance 78 which communicates with an annularfrelief ltlZrformed y in pump bodyY '74. Groovey 1Min turn communicates with the bore 72 in pump body 'ifiV via a passage 104. Bore 72 in turn communicates withV accumulator $6' Via a vertical passage 196 formed in the base of pump body 74. A pair of check valves 1% and 11l.are located v t1onwith uppergroove 80 Vand passage 90 enabling uid formed in thefspool` valvefis Abrought Vintopartial registracontained in space 94 to moveupwardly. through passage 92' and and `rennerge throughrpnort84;Y into the reservoir 'IAS hydratant: sind eaters nespace, yimir 24 is hy-pv d raulicallydisplaced,downwardlyrelative topiston 28 until plunger-44 yis retirnedvto the normal positionshown in FIGURE'ZQatiw/hich time spool valve 5,4,is restored, to

respectively in bore and adjacent bore I166 for a purpose shortlyy to be described.y

The upper portion Vof bore 42 betweeiipump ,body 74` and bore 40 is placed in liuid communicationwith reserf,`

voir 36by a passage 112 having a restriction oriiicefllfl formed therein. rA passage 116 extends through. theV iiangeAV piston 68 to establish comrnunication between the` ne neutral'V position bythe action of coil Vspring 56,-.

By referencefto FIGURE jl, it will l be seen that the direction of movement Aoffplunger 44 is mechanically corre- 'lated with relativer displacement between the. vehicle sprung and lunsprurig';nia/ss meansfcf apiv'ote'd drop link which -isjco'nnectedV at 'its opposite 'ends to lower Y controlfarrn V12fan'd thefreeend'of lever 48y respectively.

Since, as previously described, downward movement of plunger 44 results in hydraulic displacement of cylinder 24, it will be evident that an iincrease in load on the sprung mass will result in movement of link 130 upwardly relative to the sprung mass and thus urge the plunger in the downward direction causing hydraulicextension of cylinder 24 to occur with the result that the sprung mass is ultimately restored to the normal vertical level. Naturally, as the sprung mass rises, link 130 progressively restores the plunger to the neutral position and terminates the leveling action as previously described. Conversely, an increase in the height of the sprung mass causes the plunger to move upwardly and actuate the spool valve to the exhaust position previously described. To accommodate momentary extremes in vertical deflection of control arm l2, link 139 includes a two-way resilient connection 132 which allows movement of the arm beyond the mecahnical limits of travel of plunger ed. Resilient connection 132 comprises a pair of coil springs i3d and 136 caged in the sleeve end 138 of the upper rod portion 40 which act in opposition to the flanged end 142 of lower rod portion 144.

inasmuch as vehicle suspension experiences both sustained and short term intermittent deflection, it will be evident that the leveling function occurs only upon sustained deflection equal to or greater than the time rate delay in response produced by the dashpot action previously described. However, during normal operation of the vehicle, a limited but almost continual short range and duration deilection occurs which causes the plunger dit to constantly reciprocate relative to piston 28. in the present invention, the short term reciprocation of plunger 44 is utilized to operate the pump '74 to return hydraulic fluid from the reservoir to the accumulator chamber. In the illustrated embodiment, this is accomplished in the following manner. As the lower end ldd of plunger fill descends in bore '72 of pump 74, any fluid already contained therein is discharged into accumulator chamber S6 through passage we. Upon upward movement of the plunger, return of the fluid through passage No is prevented by check valve 11?. However, the upward movement or plunger 44 creates a partial vacuum in the space 146 between the lower end of plunger 44 and the base of bore '72 which causes iiuid in reservoir 36 to displace check valve 108 and enter the bore 72. Return downward movement of the plunger repeats the displacement mode previously described while check valve :i955 prevents return of the fluid to reservoir 3d. Therefore, short range wheel deflection typical of normal vehicle operation produces a continuous small displacement pumping action which constantly returns any fluid in the reservoir to the accumulator chamber where it is available for repetition of the leveling action previously described. In the event that no leveling action is required for long periods of vehicle operation, the pump '74 is prevented from pumping the entire contents of the reservoir into the accumulator chamber by the provision of a relief valve 133 which is set at a predetermined pressure above which fluid in accumulator 86 is allowed to return to the reservoir.

While but one embodiment of the invention has been shown and described, it will be apparent that other changes and modifications may be made therein. It is, therefore, to be understood that it is not intended to limit the invention to the embodiment shown, but only by the scope of the claims which follow.

l claim:

l. in combination with a coil spring disposed between the sprung and unsprung mass of a vehicle, a hydraulically extensible spring seat assembly disposed between one end of said spring and the adjacent mass, said assembly comprising a piston element iixed to said mass, a cupshaped cylinder telescopingly engaging said piston element to form a variable volume fluid cavity therebetween, a fluid reservoir formed in said piston element7 a first fluid circuit between said reservoir and said cavity, a fluid pressure chamber formed in said piston element, a second fluid circuit between said cavity and said chamber, a spool valve slidably disposed in said piston element movable in a path intersecting said first and second fluid circuits, la plunger slidably mounted in said piston element extending through said spool valve, linkage means operatively connecting said plunger to said unsprung mass, `a coil spring connecting said spool valve and said plunger so that said spool valve is urged to a neutral circuit blocking position when said plunger is in a predetermined neutral position relative to said piston element while movement of said plunger in opposite directions therefrom acts through said spring to open said first and second circuits respectively, a third fluid circuit between said reservoir and said pressure chamber, a pump body disposed in said piston element in alignment with said spool valve and intersecting said third fluid circuit, means on said plunger forming a pump piston, and a deformable container in said chamber filled with compressible fluid under pressure.

2.. ln combination with a coil spring disposed between the sprung yand unsprung mass of a vehicle, a hydraulically extensible spring seat assembly disposed between one end of said spring and the adjacent mass, said assembly comprising a piston element fixed to said mass, a cupshaped cylinder telescopingly engaging said piston element to form a variable volume fluid cavity therebetween, a fluid reservoir formed in said piston element, a rst fluid circuit between said reservoir and said cavity, a fluid pressure chamber formed in said piston element, a second fluid circuit between said cavity and said chamber, a spool valve slidable relative to said piston element in a path intersecting said first and second fluid circuits, a plunger slidably mounted in said piston element extending through said spool valve, linkage means operatively connecting said plunger to said unsprung muss, a coil spring connecting said spool valve and said plunger so that said spool valve is urged to -a neutral circuit blocking position when said plunger is in a predetermined neutral position relative to said piston element while movement of said plunger in opposite directions therefrom acts through said spring to open said first and second circuits respectively, a third fluid circuit between said reservoir and said pressure chamber, a pump body disposed in said piston element in alignment with said spool valve and intersecting said third fluid circuit, means on said plunger forming a pump piston, a deformable container in said chamber filled with compressible iiuid under pressure, and means for retarding the rate of response of said spool valve to movement of said plunger.

3. ln combination with a coil spring disposed between the sprung and unsprung mass of a vehicle, a hydraulically extensible spring seat assembly disposed between one end of said spring and the adjacent mass, said `assembly comprising a piston element fixed to said mass, a cupv shaped cylinder telescopingly engaging said piston element to form a variable volume fluid cavity therebetween, a fluid reservoir formed in said piston element, a first fluid circuit between said reservoir and said cavity, a fluid pressure chamber formed in said piston element, a second fluid circuit between said cavity and said chamber, a spool valve slidable relative to sai-d piston element in a path intersecting said first and second fluid circuits, a plunger slidably mounted in said piston element extending through said spool valve, linkage means operatively connecting said plunger to said unsprung mass, a coil spring connecting said spool valve and said plunger so that said spool valve is urged to a neutral circuit blocking position when said plunger is in a predetermined neutral position relative to said piston element while movement of said plunger in opposite directions therefrom acts through said spring to open said first and second circuits respectively, a third fluid circuit between said reservoir and said pressure chamber, a pump body disposed in said piston element in alignment with said spool valve and intersecting said third lluid circuit, means on said plunger forming Yapump piston,

a deformable container in said chamber filled with compressible fluidunder pressure,`a dashpot acting on said Y spool valve to Aretard therate of movement thereof, and a two-way resilient connection in said'linkage means.

4. The Structure set forth in claim 3 wherein saidtwo-'fY way resilient connection includes a coil spring having a higher rate than Ythe rate of the coil spring connecting said plunger and'spool valve. Y i n y Y:

5. A self-energizing hydraulic leveling device compris-V ing, Ia xed'element, a movable element arranged in telescoping yrelation with said Xed element, means' forming a space between said elements adapted to cause relative axial movement therebetween upon introduction of hydraulic fluid therein, a pressurized lluid chamber contained within said xed element, passage means providing com-v munication between said chamber and said space, a Huid reservoir ycontained withinr saidl fixed element, passage means providing communication between said space and said reservoir, valve means displaceable. in opposite directions from a neutral position interrupting communication between said space andsaidfreser-voir and betweenv said chamber and said space movablel toV Va rst position enabling communication from said chamber Ito said space only and to a second position enabling communication from said space tolsaid reservoir only, means including a pump providing communication between said reservoir vand chamber, a common operating element for said valve means and said pump,'and means mounted externally of said iixed elementfor actuating said common element.

,30, 972,828 6. A self-energizing hydraulic leveling device 'compris-i ing, a fixed element a movable element arranged'intele- 10 opposite directions from a neutral position interrupting communication between said space and said reservoir and between said chamber and said'space movable to a lirst position enabling communication from said chamber to said space only and toV a second position Yenabling com- 15 munication from saidspacefto said reservoironly, means including an axial displacement pump providing communication between said reservoir landchamber, a com- Vmon axially displaceable operat-ing'element for said valve means and said pump, and meansmounted externally of 0 said lixed element for vactuating said. common'element.

References Cited bythe Examiner UNITED ysr'Ares@Partants 2,571,449 V10/51 Hobbs Q 267-60 2A, '2,818,311 12/57 Ash1ey f V 267-605( 2,935,313 YV5 /60 Momhi10veria1. a 267-2o YFOREIGN PATENTS ,536,263A S/41 Great Britain. Q,

'10/ 579 Germany.,

'I ARTHUR L. KLA* POINT, Primary Examiner. i 

5. A SELF-ENERGIZING HYDRAULIC LEVELING DEVICE COMPRISING, A FIXED ELEMENT, A MOVABLE ELEMENT ARRANGED IN TELESCOPING RELATION WITH SAID FIXED ELEMENT, MEANS FORMING A SPACE BETWEEN SAID ELEMENTS ADAPTED TO CAUSE RELATIVE AXIAL MOVEMENT THEREBETWEEN UPON INTRODUCTION OF HYDRAULIC FLUID THEREIN, A PRESSURIZED FLUID CHAMBER CONTAINED WITHIN SAID FIXED ELEMENT, PASSAGE MEANS PROVIDING COMMUNICATION BETWEEN SAID CHAMBER AND SAID SPACE, A FLUID RESERVOIR CONTAINED WITH SAID FIXED ELEMENT, PASSAGE MEANS PROVIDING COMMUNICATION BETWEEN SAID SPACE AND SAID RESERVOIR, VALVE MEANS DISPLACEABLE IN OPPOSITE DIRECTIONS FROM A NEUTRAL POSITION INTERRUPTING COMMUNICATION BETWEEN SAID SPACE AND AID RESERVOIR AND BETWEEN SAID CHAMBER AND SAID SPACE MOVABLE TO A FIRST POSITION ENABLING COMMUNICATING FROM SAID CHAMBER TO SAID SPACE ONLY AND TO A SECOND POSITION ENABLING COMMUNICATION FROM SAID SPACE TO SAID RESERVOIR ONLY, MEANS INCLUDING A PUMP PROVIDING COMMUNICATION BETWEEN SAID RESERVOIR AND CHAMBER, A COMMON OPERATING ELEMENT FOR SAID VALVE MEANS AND SAID PUMP, AND MEANS MOUNTED EXTERNALLY OF SAID FIXED ELEMENT FOR ACTUATING SAID COMMON ELEMENT. 